This disclosure relates to cooling of a motor for a centrifugal compressor of a refrigeration system. Centrifugal refrigerant compressors are known, and include one or more impellers driven by a motor. The motor in some examples is an electric motor including a rotor and a stator. In one known example the motor is cooled by circulating refrigerant about the stator, to cool the stator, and then directing that refrigerant between the rotor and the stator to cool the rotor. After cooling the rotor, the refrigerant is returned to a refrigeration loop.